The GTPase superfamily, which is composed of the heterotrimeric and ras- related subclasses, has become a central focus for studies aimed at understanding growth control and receptor signal transduction. In addition, recent evidence suggests that these proteins play central regulatory roles in diverse cell functions such as membrane regulation, secretion endocytosis, and protein trafficking. The Core Director has adapted the use of these approaches to the study of GTP binding proteins in cell function. The use of needle microinjection to introduce defined amounts of purified proteins, expression plasmids, and inhibitory antibodies and small molecules, into living somatic cells such as fibroblasts is a powerful tool to aid in the analysis of the functional roles of cellular proteins. We have assembled a core facility which will give access of this technology to the investigators of this PPG application who work in the analysis of membrane trafficking. Experiments, have already begun to facilitate this transfer of technology to this group. Accordingly, the aims of this core are: 1. to provide the technical capability for somatic cell microinjection 2. to provide aid in the design of experiments and in the required subsequent biological and biochemical assays for effects in the injected cells. 3. to train investigators in the use of this approach. In addition, the group will work to explore novel assays related to the analysis of membrane trafficking through the combination of diverse expertise's that exist within this group.